The invention arose during development efforts relating to amplitude detectors for secondary radar systems for filtering out replies responding to other systems, i.e. FRUIT, friendly replies to unintentionally interrogated targets, though the invention is not limited thereto.
It is known in the prior art to filter out some of the FRUIT by establishing a minimum threshold voltage that the reply video signal must exceed in order to be accepted. The problem with this system is that there is no upper limit.
The present invention provides a system which establishes both minimum and maximum limits that the reply video signal must be between in order to be accepted.